The present invention relates in general to integrated circuits, and more particularly to high frequency filtering devices which are integrable with other electrical components.
The demand for wireless communication services is rapidly increasing, so that many frequency bands for cellular telephone and other services are operating at or near their capacities. To accommodate future growth, additional frequency bands are being allocated, but at higher frequencies than existing bands. For example, cellular telephone systems currently operate at frequencies up to 2.4 gigahertz, whereas future systems are expected to operate at 5.8 gigahertz or more.
Many of the components used in portable wireless devices suffer from either a high cost or poor performance at the higher frequencies. For example, cellular telephones use surface acoustical wave (SAW) devices to filter RF carrier signals. However, SAW devices have a high insertion loss, which degrades RF signals and results in poor performance of cellular telephones. Moreover, SAW filters are not commercially available for operation at the higher frequencies.
Other types of filters are not used because of their high parts count and cost and/or their large physical size.
Hence, there is a need for a filtering device which has good performance at high frequencies and which has a low cost and compact size.